To explore PFS, ORR (CR/CRu+PR), OS and side effects of piamprizumab combined with RMA in newly diagnosed PCNSL, so as to clarify the value of piamprizumab combined with RMA in the first-line treatment of PCNSL patients, and to clarify the clinical and biological factors affecting the efficacy

Inclusion Criteria:

• For initial PCNSL confirmed by pathological tissue, the diagnostic criteria were based on WHO diagnostic criteria in 2016
• Head MR (plain scan + enhancement) performed 28 days prior to study enrollment should show the presence of at least one measurable lesion in two vertical directions (according to 2014 Lugano criteria); Or abnormal cerebrospinal fluid examination (including cerebrospinal fluid protein, cells, NGS), or ophthalmologic examination confirmed the retina, vitreous lesions
• PS score was 0~4 according to ECOG

Exclusion Criteria:

• Organs or lymph nodes outside the central nervous system are involved
• Patients with a second primary tumor (other than non-melanoma skin cancer in situ, superficial bladder cancer, cervical cancer in situ, gastrointestinal intramucosal cancer or breast cancer that has been cured and has not recurred within 5 years)
• Has a history of allergic disease, severe drug allergy, or is known to be allergic to any component of a macromolecular protein preparation or penpulimab injection prescription
• Prior treatment with anti-PD-1 antibody, anti-PD-L1 antibody, anti-PD-L2 antibody, anti-CTLA-4 antibody, or CAR T cell therapy (or any other antibody that acts on T cell co-stimulation or checkpoint pathways)
• A severe acute or chronic infection requiring systemic treatment
• The investigator believes that the subjects may have other factors that affect the efficacy or safety evaluation of the study